All conventional power converters require auxiliary supply for feeding the control circuitry of the power converter.
The power converter can comprise one or more power stages, wherein there are some approaches known for implementation of such auxiliary supply, which may even be combined.
One approach includes that the auxiliary supply is integrated in one or more stages of power converter (e.g. by integration into a PFC (Power Factor Correction) by means of placing an auxiliary winding on the PFC inductor), and the one or more power stages in operation as used for generating the auxiliary supply. However, if the power converter is not active, e.g. set to stand-by mode, also the auxiliary supply is cut off and the converter control circuitry is not supplied with power anymore.
Another approach includes that the auxiliary supply is not integrated but implemented as an independent part of converter (e.g. by using an additional flyback converter which is fed from, for example, the bus (or mains) voltage). This approach allows for independently delivering power to the control circuitry during any mode of operation. However, a disadvantage of this approach are increased costs due to a larger number of components required and, typically, larger costs of individual components.